Rocks that are high in bituminous matter are known as domanikites after the Upper Devonian Domanik Formation of the Volga-Ural oil-gas province. The Domanik Formation was named by Murchison, Verneuil, and Keyserling in 1845 as they were setting up the Permian System in the Perm Region of Russia. Examples of domanikites are the bituminous shales of the Bazhenov Formation of West Siberia and the clayey-siliceous limestones and dolomites of the Upper Devonian and Tournaisian of the eastern part of the Russian platform. The former are productive in Salym and other fields of West Siberia; however, the latter have not yielded significant pools as yet, although strong flows of oil have been recovered in many wells. The Upper Devonian-Tournaisian domanikites have an average carbonate content of 70 percent, clay and free silica are 10-15 percent, and sapropelic organic matter is 3-5 percent. Depending on the ratio of components the rock may be a limestone, marl, shale, or chert. Domanikites collect in uncompensated sedimentary basins. Such a basin was present in the eastern part of the Russian platform over a very wide area during Semiluka time of the Late Devonian Frasnian Stage. Subsequently in Late Devonian and Tournaisian time the dimensions of individual basins were gradually reduced to the relatively narrow troughs of the Kama-Kinel system. The high content of organic matter resulted from enrichment of the marine waters of the basin by zooplankton. According to some estimates the domanikites supplied 126 billion tons of hydrocarbons to the Volga-Ural oil-gas province. Distribution is uneven by area and along the section. Almost half is in the central region - Tataria and Bashkiria. Generating potential was lower on the southeast in Orenburg and Samara Regions and on the northwest in Perm Region and Udmurtia. A direct measure of oil potential of the domanikites of the Volga-Ural province comes from well testing. Of 1267 objectives tested as of January 1, 1986, 717 were dry, 327 yielded water,, and 223 gave flows of oil of 1 to 100 tons (7 to 700 bbls) per day. In Tataria wells have yielded as much as 40-50 tons per day in three areas: crest of South Tatar arch, north flank of this arch, and southeast flank of North Tatar arch. In Bashkortostan the domanikites are oil- bearing both on the platform and in Belaya depression of the Cis-Ural foredeep, where flows at 100-120 tons per day have been recovered. The oil potential of the domanikites diminishes with distance from the central parts of the Volga-Ural regional high, particularly to the north and northwest. To the southeast there are fewer oil-bearing areas; however, many strong flows have been brought in there. The high flows of oil from these rocks of low porosity and permeability are due to fracturing. If, however, fracturing is too great, the seal is broken; and if too little, then permeability is not enough. (Taken from Zaydel'son and others, 1990. Digested in Petroleum Geology vol. 25, no. 1-2, p. 1-3; one map.) It is generally accepted that the Domanik Formation is the source bed for the oil of Romashkino and other giant fields of the Volga-Ural oil-gas province and that the Bazhenov Formation is the source bed for Samotlor and other giant fields of West Siberia. I think that these bituminous rocks are too tight to have given up much oil. I think that the Romashkino oil was derived from other source beds down dip to the east and southeast, and that the oil at Samotlor was derived from source beds to the west that intertongue with the Neocomian reservoirs. Copyright 2000 James Clarke. You are encouraged to print out this News Letter and to forward it to others. Earlier News Letters are available at: http://geocities.com/internetgeology/ Inquiries concerning Petroleum Geology can be made at (703) 759-4487.